My 'must take' plane travel items: (12 hour flights, you betcha)
1) Small goose down pillow, crushed down into flexible courier bag for carry on (same pillow I sleep on at home, so no need to sleep on those foam cubes at the destination hotel)
2) Ear plugs. Silencio brand, silicon filled, conform to your ear. The twins behind me screaming their heads off can't cut through these.
3) Bose noise cancelling earphones. Much better sound than those provided by the airline and cut the exterior noise at the same time.
4) Kindle, loaded with good books.
5) Sweatshirt to wear at 40,000 feet when you can't turn off the a/c.

What else would you never be without on a long flight?